System of automatic offset control for traffic signals



J. N. PAUL Nov. 12, 1963 SYSTEM OF AUTOMATIC OFFSET CONTROL FOR TRAFFIC SIGNALS Filed Feb. 17, 1959 4 Sheets-Sheet l oursouuo HIGHWAY INBOUND I GE/H? 50X) 05 OFRSE T JELECTOR 5 T (.SHMPLING TIMER) 6C (SIFLECTOR CUTOUT (GT/MEGA INVENTOR e 2 I ATTORNEY) SYSTEM OF AUTOMATICOFFSET CONTROL FOR TRAFFIC SIGNALS Filed Feb. 17, 1959 J. N. PAUL Nov. 12, 1963 4 She e ts-Sheet 2 Nov. 12, 1963 I J. N. PAUL 3,110,881

SYSTEM OF AUTOMATIC OFFSET CONTROL FOR TRAFFIC SIGNALS Filed Feb. 17, 1959 4 Sheets-Sheet s OUTBOUND ------HIGHWHY fi vplfl INBOUND MHSTER I co/vmousn I I VI 5 3 I 05 LRI I OFFSET LATCH I I SEL'CTOR RELAY I -11} I I I/z H I ,Z I s T LRO I 1z I SAMPLING LATCH I 0 I H4. TIMER RELm II 'I I I I SR TR I I I" I sascron TIMING I I I I RemYs nwuarm I CT 56 I I I I I CHLCULRTING sazcr I I I I 77MER CUTOUT I I T I I J I SIGNHL TIMER I 0c (OFFSET CONTROLLER) I I I s I SIGNALS I J BYq ATTORNEYS J. N. PAUL 3,110,881

SYSTEM OF AUTOMATIC OFFSET common FOR TRAFFIC SIGNALS Nov. 12, 1963 4 Sheets-Sheet 4 HIGHWAY Filed Feb. 17, 1959 OUTBOUND INBOUND I l I ErEcToR) G INBOUND ATTORNEYS United States Patent signments, to The Garnewell Company, Newton, Mass,

a corporation of Delaware Filed Feb. 17, 1959, Ser. No. 793,710 Claims. (Cl. 340-) This invention relates in general to improvements in electrical circuits and devices for controlling signalling apparatus, and especially for controlling a plurality of signals arranged in a coordinated groupor system. A common example of such a group is a series of signals along a traffic artery leading from a residential'to a business district. Another example is a district in (which a group of parallel streets running north and south is crossed by streets running east and west where it is desirable to coordinate traffic flow in the entire district. Many cities due to waterfront or terrain restrictions have very irregular street layouts and frequent local areas requiring special treatment.

Traflic moves most efficiently in what is known as a progressive system, and in setting up such a system provision must be made for dividing the time at each intersection in a manner best suited to accommodate the traffic, and provision must also be made for setting the relative timing of offsets of the green indications. Progressive systems are in common use, some of which provide a selection of offsets to adapt the apparatus to'changes in tramc and some provide a limited selection of timing divisions or splits, and some provide means for changing the total cycle length, these adjustments or manipulations being possible by remote control from a central station.

This invention is directed more specifically to improvements in offset control and the tie-in betweenoifset control, cycle length control and cycle split control.

It is frequently advantageous to change offset in only a portion of a signal system or even to provide for independent offset changes in several portions of a system. These could be considered as satellite offset controls. The relatively inexpensive offset selector equipment with its relatively inexpensive installation cost is a distinct advantage of the invention of the present application as will be clear from the description and claims that follow.

It is common practice to provide three offset selections, one of these offsets favoring inbound trafiic, one favoring outbound traffic, and one giving equal advantage to both. There is, however, a period in the early morning hours beginning frequently at about midnight when traffic is very light when any one of the three usual olfsets even combined with the shortest practical cycle length imposes an unnecessary speed restriction. It is common practice under such conditions to switch all signals to flashing indication. My invention provides for a fourth offset which can be used to meet this condition which can be adjusted to permit traffic to move at the maximum safe speed and still have full signal protection.

My invention is not limited to four offsets. It can, for example, be expanded to provide two instead of one offset for inbound and the same for outbound traffic. The system is not inherently limited to any specific number of offsets.

Further objects and advantages will be pointed out or become apparent as the description proceeds.

In the accompanying drawings:

FIG. 1 is a diagram showing a form of control apparatus embodying the invention;

FIG. 2 is a detail showing a modification applicable to the diagram shown in FIG. 1;

FIG. 3 is a detail showing a further modification applicable to the diagram shown in FIG. 1;

FIG. 4 is a detail showing a further modification applicableto the diagram shown in FIG. 1;

FIG. 5 is a block diagram showing the equipment indicated in FIG. 1 as connectedinto a complete signal system;

FIG. 6 is a diagram showing a modification of the control apparatus embodying the invention; and

FIG. 7 is a block diagram showing the equipment indicated in FIG. 6.

The diagram of FIG. 1 has been prepared in an acrossthealine form in which the main lines of the power supply P and C are shown at the left and right sides respec-' tively. P and C represent power supply from a master timer which may be in the form of a variable frequency, a pulsating current, a variable voltage or other means by which cycle length control may be transmitted from a master controller to units at local control points throughout a system.

At the upper part of FIG. 1 is represented a highway with arrows indicating the outbound and inbound traffic lanes. A detector DI is shown in the inbound lane only. Below the detector is shown schematically a time element relay or the equivalent TEI. In the power feed to the detector is shown schematically the usual transformer TR to provide a voltage convenient for use in the detector. Below the time element relay and the transformer is shown otfsetselector OS. Below OS are shown asampling timer ST and a calculating timer CT. Below these units is a selector cutout SC and at the bottom are shown latch relays LRI and LRO.

The offset selector OS is a unit in which R represents the rotor of a motor (the well known induction disk type being assumed as convenient) equipped with {four driving elements 11, 12, 13 and 14 of the well known shading pole piece type. These driving elements are arranged each to produce torque on the rotor in the direction indicated by the accompanying arrows. G represents conventionally a gear reduction train. Cams 5, 6, 7, 8, 9 and 10 are mounted on a cam shaft 36 driven by the motor through the gear reduction G The cams 5, 6 7, 8, 9 and 10 control contacts 15, 16, 17, 18, 19 and 26' respectively. A stop pin 21 shown for convenience on cam '5 comes in contact 'with stop 22 limiting the rotation of the cam shaft.

The samplingtimer ST consists of a motor with rotor R connected through a gear reduction G to a cam shaft 37 on which are mounted cams 31, 31 32 and 33. Contacts 41, 4d, 42, 4-3 and 44 are controlled by the cams as shown.

The calculating timer CT consists of a motor with rotor R connected through a gear reduction G to a cam 34. Contacts 45, 46 and 47 are arranged to operate from cam 34 as shown.

The selector cutout SC consists of two motors with rotors R and R connected through gear reductions G and G respectively to a differential 35. As indicated by the arrows, both rotors rotate in the same direction. Rotor R is driven at constant speed but R is driven at a variable speed proportional to the cycle length of the system. Arm 49 is carried by the member that carries the idler gears of the differential. If R runs relatively faster than R arm 49 will be carried in the direction toward stop 54) while if R run relatively faster than R arm 49 will be carried in the direction toward stop 51. Arm 49 is limited in its movement by stops 5i) and 51. When arm 49, as shown in the circuit of FIG. 1, is against stop 50, contact 43 is closed and, when against stop 51, contact 48 is open. As shown in the circuit of FIG. 3, when arm 49 is against stop 5%), contacts and 61 are open and,

' when arm 49 is against stop 51, contacts 60 and 61 are closed. The motors used are of a well-known type that will not be harmed by repeated or continuous stalling.

Rotor R is driven from a power supply PC through lead 79 connected to P, contact 43, lead 73, contact 45, lead 55, coil 89 and lead 71. Rotor R is driven from the same power supply PC through lead 73, coil 96 and lead 79. Power supply P'C' can be a variable frequency, a pulsating current, or any other means of maintaining the operation of intersection controllers on the cycle length established by the master controller.

LRI and LRO are latch relays which open and close ofiset control circuits 2 and 3 as will be described later.

PEG. 2 is a modification of the latch relay control circuit applicable to FlG. l. Selector cutout SC and connections 78, 73 and 86 have been omitted. Connection 84 connected directly to line P replaces connection 84 and supplies power direct to contacts 27 and 28 instead of through contact 48 and connection 83.

FIG. 3 is a modification of a selector circuit applicable also to the circuit of FIG. 1. In the modified selector cutout MSC contact 48 has been replaced with two contacts 6% and 61 which are closed when arm 49 is against stop Sll and open when arm 49 is against stop 56. Latch relays LRO and LRI in FIG. 3 are the same as in FIGS. 1 and 2. Selector relays S and S show a typical means of selecting any one of four circuits from two control circuits. This typical arrangement of relays is applicable to the circuits of FIGS. 1, 2 and 5 except that in these circuits, as shown, lines 2 and 3 are never energized at the same time so circuit L would not function but with the connection shown in FIG. 3 line L can be energized as will be explained later.

FIG. 4 is a modification applicable to the circuit of FIG. 1. Coil 96 receives a constant energy supply from power source P through lead 38 and lead 86 Coil 98 receives power from the variable power supply P through lead 73 and lead 79 The results accomplished by this modification will be explained later.

FIG. 5 is a block diagram showing my invention of an offset controller as associated with other units to make up a complete operating system. The master controller MC may be any of the various types used to establish and maintain the cycle length for the system. It may be of the so-called pre-timed type in which no provision is maderfor change in cycle length but preferably is of a type providing cycle length adjustment by traflic actuation, by program instrument or by manual manipulation. The offset controller OC shown in block form consists of the same units as shown in the wiring diagram of PEG. 1 and is subject to the modifications shown by F163. 2, 3 and 4. The local signal controller LSC may be any one of the various types available that will respond to changes in offset, a preferred type being as disclosed in my Patent No. 2,657,- 375. The signals S may be of any approved type.

FIG. 6 is a modification of the invention shown in FIG. 1. Calculating timer CT is omitted and also cam 33, contact 43 and connections 70, '71, 72, 73, 74 and 75. Detector D in the outbound lane has been added with time element relay TEO and connections 76 and 77 to coil 12. The modifications shown by FIGS. 2, 3 and 4 are applicable to the circuit shown by FIG. 6.

FIG. 7 is a block diagram of the modified offset controller MOC shown by FIG. 6, modified as shown by FIG. 2. Controller MOC ties in with a master controller MC, local signal controller LSC and signals S in the same manner as is shown in FIG. in connection with offset controller OC.

Referring to FIG. 1, offset control is as follows:

Assume that the sampling timer ST is just at the point of starting a sampling period at which time cams and contacts in ST, OS and CT would all be in the positions as shown. The sequence of operations will explain how this is brought about. Let us assume that the cycle length established by the master for the system is longer than the minimum of the range provided. On all cycle lengths except the minimum, contact :3 will be closed.

Operation on minimum cycle will be explained later. The positions of contacts 27 and 28 would depend upon conditions in the next preceding sampling period but the position as shown with both open could be a nautral con dition and will be assumed for this example.

Rotor R is driven preferably at synchronous speed and, through change gears in G can be made to drive cam shaft 37 at any desired speed. The exact speed of cam shaft 37 is not critical so an adjustable speed drive of R with elimination of change gears in G could be substituted. Cam shaft 37 with the arrangement of cams shown makes one revolution in a sampling period. This period can be of any appropriate length but is preferably a multiple of the maximum cycle length provided for the system. In this example let it be assumed that the maximum cycle for the system is seconds and that the sampling period is 5 70=350 seconds-a practical length. If 5 is used as a multiplier applied to the maximum cycle length to establish the sampling period of 350 seconds, the number of lobes on cam 33 would also be a multiple of 5. Cam 33 has 20 lobes in the example assumed for reasons which will become apparent.

At the start of the sampling period contact 44 closes, supplying energy from power source P to detector DI through lead 52, lead 195, lead 87, transformer TR and lead 88. Contacts 43 and 47 would be open so no energy would reach driving coil 89. Rotor R runs continuously on energy from power source P through lead 52, lead 53, coil 31) and lead 54 so very soon contact 43 would close, energizing the driving coil 89 of rotor R through contact 45, lead 73, contact 43, and lead 7 ti from power source P. A small movement of rotor R rotates cam 34 a small amount through the mechanical connection of gear train G This closes contact 47 energizing driving coil 89 of rotor R from power source P through lead 70, lead 72, contact47, lead 55, coil 89 and lead 71.

Contacts 47 and 45 are a make before break combination so after contact 45 breaks contact 47 will continue to energize coil 89 until cam 34 advances a quarter turn to the next notch which will open contact 47 and close contact 45. As an example let us assume that the system is operating on a 60-second signal cycle in which case cam 34 will rotate at a speed of l revolution in 60 seconds while in motion or, as there are 4 lobes and 4 notches, will require 15 seconds to advance from one notch to the next. During this interval contact 46 will be closed. This will apply direct energy from power source P through lead 52, contact 44, lead 105, lead 74, contact 46 and lead 7 5 to coil 12. During the time that cam 34 is making a Mr turn, contact 43 opens. Cam 33, which controls contact 43, turns at the rate of 1 revolution in 350 seconds in the assumed example and, as cam 33 has 20 lobes, it will advance a space of one lobe in 17 /2 seconds. After cam 34 has advanced one lobe which requires 15 seconds, as explained above, it cuts off its own driving energy by the opening of contact 47 and at the same time closes contact 45. Before coil 89 of rotor R can again be energized, it must wait for contact 43 to close which, as explained, occurs at intervals of 17 /2 seconds. The overall result is that cam 34 which controls contact 46 as well as contacts 45 and 47 closes contact 46 for 15 seconds and must then wait the difference between 15 and 17% seconds or 2 seconds before it can close again. The process continues with contact 46 closed for 15 seconds during each l7 /2-second interval which energizes coil 12 for 15 seconds out of each 17 /z-second interval. The ratio of time that coil 12 is energized is 15 to 17 /2 which is exactly the ratio of operating cycle to maximum cycle or 60 to 70. In other words, coil 12 is energized 9' of the time in a 60-second cycle.

A vehicle actuating a detector usually closes the detector contact once for each axle. In equipment used in this example the impulse of the first axle of a vehicle to pass the detector registers on the time element relay and initiates a time period of a length convenient to apply to a driving coil of rotor R to obtain the action desired. This time period is usually of the order of one or two seconds. Axles on any vehicle after the first axle usually pass the detector during this lengthened period and are ineffective. In the present example it is assumed that each vehicle causes one effective impulse in passing each detector. Exceptions would be rare and negligible.

Assume for convenience that a trafilc density of from 135 to 145 cars per sampling period adjusts the cycle v length to 70 seconds and that a traffic density of from 115 to 125 cars per sampling period adjusts the cycle length to 60 seconds. Coil 12 when energized continuously is adjusted by its shading pole piece to balance impulses on coil 11 at the rate of 70 per sampling period. At a 60- second cycle the time, during which coil 12 is energized, is of the total which, without changing the adjustment of coil 11, will just balance detector impulses at the rate of 60 per sampling period. The balance will be similarly established at all cycles. Any desired ratio of total traffic'to cycle length may be balanced by adjustment of the shading pole pieces of coils 11 and 12 and using a suitable gear ratio in G which preferably is equipped with some standard form of change gears.

Assume now that the system has been adjusted so that coil 12 torque balances the torque produced in coil 11 by 60 impulses per sampling period from timer TEI actuated by 6t) cars passing detector Dl. if now the traffic in the inbound lane over detector DI is at the rate of more than 60 cars per sampling period, the torque produced by coil 11 will overbalance that of coil 12 and cam shaft 36 will rotate in the direction of the arrow of coil 11. The relative torques produced by coils 11 and 12 may be adjusted by means of their shading pole pieces so that a predetermined excess of cars, for example, passing detector D1 will rotate cam shaft 36 so that pin 21 engages stop 22 and contact closes, which energizes coil 23 from power source P, lead 1%, contact 15, and lead 82, which closes contact 27 of relay LRL T his closes the circuit from power source P through lead 85, contact 48, lead 84, lead 97 and contact 27 which energizes line 2. This selects the oifset favoring inbound traffic by any of the well known methods, for example as disclosed by my Patent No. 2,657,375.

A relatively short time before cam shaft 37 of the continuously operating sampling timer completes a revolution, cam 32 opens contact 44. This cuts off energy to coil 11 through lead 165, lead 87, transformer TR, lead 88, detector DI, lead 56, time element TE! and lead 57. The only source of energy to coil 11 is through detector DI so, while contact 4.4 is open, coil 11 will receive no energy. The only source of energy to coil 12 is through contact 4-4, lead 1%, lead, 74, contact 46 and lead 75 so when contact 44 is open coil 12 also will receive no energy. The same operation of cam 32 that opens contact 44 closes contact 42. This energizes lead 91 from power source P through lead 52 to contacts 17 and 18. in the preceding paragraph a sequence of operations has been followed to bring cam shaft 36 to the position to close contact 15. in this position contact 17 would be open and contact 13 would be closed, energizing coil 14 from power source P through lead 52, contact 42, lead 91, contact 18 and lead 93. This will exert torque in a counterclockwise direction and return cam shaft 36 to the position as shown which is the position assumed for the start of a sampling period. This is called a resetting period.

A sampling period is considered and referred to as th time in which cam shaft 37 of sampling timer ST makes one complete revolution. During the resetting period just referred to actual sampling is stopped by the opening of contact 44 by cam 32. This cuts ofi power supply P to coil 11 by the only path through lead 1%, contact 44, lead 8 7, transformer TR, lead 88, detector D1, lead 56, time element relay T131 and lead 57. Also opening of contact 44 cuts off power supply P to coil 12 through lead 6 52, contact 44, lead 195, lead 74, contact 46 and lead '75. The resetting period is a relatively short portion of the total sampling period. Cutting ofi actual sampling during the resetting period does not distort'the sampling but is in reality a short interval between true sampling periods.

it should be noted that in the position of cam shaft '36, as shown, contacts 17' and 1% are both shown closed. T1 is, however, is for a very short angular movement and serves the desired purpose of energizing coils 13 and 14 at the same time. Coils 13 and 14 which return the cam shaft to the position shown are set to drive rotor R at maximum speed so the resetting peniod will be as short as possible. When coils 13 and 14 are energized at the same time, they each act as a brake on the other, restricting coasting and overrunnin-g, thus bringing rotor R to a quick stop.

It has been explained above how coil 23 of latch relay Lill was energized, closing contact 27. Relay LRI is of the type that, when contact 2'7 is closed, it will be locked closed by latch 2% and remain closed even if the actuating coil 23 is d e-energized. in the example so far all contacts have been returned to the assumed starting position except contact 27 and contact which is actuated by the same means as contact 27. The function of contact 39 will be explained later. 7

If in succeeding sampling periods traffic over detector D1 equals or exceeds the predetermined excess of 10 cars, the above sequence of operations will be repeated in each sampling period and the offset favoring inbound traffic will continue in effect. Coil 23 will become energized during each sampling period but contacts 27 and 39 will remain closed.

Assume now that in a sampling period the number of cars over DI does not reach the assumed excess of 10. Cam shaft 36 will then not rotate far enough for contact 15 to close. Contacts 19, 2t), 41 and 41 have not been previously mentioned because in the preceding they have performed no functions. They control circuits to the unlatching coils 25 and 26 of latch relays LRl and LRO. Contacts 41 and 41 both close for a short time at the beginning of the resetting period. Contacts 19 and 20 open for short ranges of movement of cam shaft 36 near the limits established by stop pin 21 and stop 22. If cam shaft 3 5 does not rotate far enough in a sampling period for contact 15 to close, contact 19 Will not open. Under this condition, if the sampling timer starts a sampling period, contact 41 will close while contact 19 is still closed. This will complete the circuit to coil 25 from power supply P through lead 52, contact 41 lead 94, contact 19 and lead 3 1. This will unlatch relay LRl and open contacts 2'7 and 39. Opening of contact 27 will de-energize line 2. Line 3 has been so far and still is de-energized so we now have the condition of lines 2 and 3 both de-energized which selects the offset favoring balanced trafllc by means commonly employed.

At the end of the resetting period just described in which contacts 27 and 39 were opened, all contacts and circuits have been restored to the positions as shown. Assume now for example that traffic over DI decreases to less than 50 cars per sampling period. It has been explained how torque producing by coil 11 by 60 cars per sampling period just balances torque produced by coil 12. If now the number of cars over detector D1 is reduced below 60, the'torque of coil 12 will overbalance the torque of coil 11 so that cam shaft 3 6 will be driven in the direction indicated by the arrow at coil 12. If the unbalancing is as great as would be produced by 50 cars or less per sampling period, for example, cam shaft as will be driven in a counterclockwise direction until stop pin 21 engages stop 22. Cam 6 will then close contact 16 and complete the circuit from power source P through lead 1%, contact 16 and lead 83 to coil 2%. This will close contact 25 which will close the circuit from power source P through line 35, contact 48, lead 34, lead 59 and contact 28 energizing line 3. This selects the offset favoring outbound traflic by any of the well lcnown selecting means. In successive sampling periods in which traffic over detector DI does not exceed the assumed 50 cars, relay 2-4 will continue in the latched position and offset favoring outbound traffic will continue in effect.

Assume now a sampling period in which the number of cars over detector DI exceeds 50 but is less than 70. in this case cam shaft will not rotate far enough in either direction to close either contact 15 or 16 or open either contact 19 or 2% Under the condition of contacts 19 and 2% being closed when the sampling timer momentarily closes contacts ill and 41 in the resetting period,

ircuit will be closed to coil 25 from power source P through lead 52, contact 41*, lead 94, contact 19 and lead 81, and to coil 2% through lead 52, contact 41, lead 95, contact 21), lead 8 and lead 68. This will unlatch either relay LRI, LRQ or both if they are in the latched position and open contacts 27 and 2d, de-energizing l mes 2 and 3, which is the condition for selecting the offset favoring substantially balanced traific in both directions.

Contact 39 has been mentioned previously as being closed whenever coil 23 of latch relay LRl is energized. Contact 49 is closed when ever coil 24 of latch relay LED is energized. Contacts 3h and 49 have performed no functions in the examples so far. it has been explained how olfset control can be transferred automatically from an offset favoring inbound trafiic to an offset favoring substantially balanced traflic and then to an offset favoring outboard traffic and back to an offset favoring balanced traffic. it would be unusual but not impossible to have a condition calling for a change directly from the offset favoring inbound traffic to the offset favoring outbound trafiic or the reverse. In such a case outboard offset could be called for before the inbound offset control circuit was released. To prevent such a conflict as having contacts 27 and 258 closed at the same time, energy is carried from. power source P through lead lili contact 39, lead 53, and lead 6?: to coil 26 of relay LRO and energy is carried from power source P through lead 69, contact all, lead 1&2 and lead i al to the unlatching coil 25 of relay LRI. This prevents either relay from closing its contacts without releasing the other. A condition will be explained later under which relay coils 23 and 24 close their respective contacts at the same time, but in the circuit previously explained and as shown by FIG. 1 such a condition would cause confusion.

The net result of the preceding is that ofiset is automatically selected to fit traffic conditions. It is assumed that cycle length is adjusted from time to time to best handle the volume of trafiic. The calculating timer automatically adjusts itself to the cycle length and controls the torque in coil 11 of the offset selector OS to an amount proportional to the cycle length which serves as a standard of comparison. impulses from a detector in one lane only oppose the standard of comparison. If they exceed by a chosen amount, an oifset is selected to favor the lane in which the detector is located. If they fall short by a chosen amount, it shows that the volume of traffic in the opposite direction is heavier and an offset is selected favoring that traffic. if traffic over the detector is within the high and low limits chosen, it indicates that traffic is substantially balanced and an offset favorable to balanced trafiic is selected.

In the example so far it has been assumed that the cycle length established by the master for the system was longer than the minimum of the range provided. Under this condition selector cutout SC performs no function and its contact 48 remains closed. A condition will now be assumed in which the system is operating on the minimum cycle length provided by the master timer and in which selector cutout SC does function.

Rotor R is driven by energy from constant power source P through lead 85, lead 38, driving coil 98 and lead 36. Rotor R is driven by energy from variable power source P through lead '78, coil 96 and lead 79. Rotors R and R are connected through gear reductions G and G respectively to differential 35. Rotors R and R both drive in the same direction but, if rotor R is driven relatively faster than R4, arm 49 on the differential will be carried against stop 5%) which will close contact 48. Gear ratios are arranged so that this is the condition at all cycle lengths longer than the minimum for which the system is regulated and which has been the condition in the example so far.

A condition will now be assumed in which the system is operating on the minimum cycle length provided by the master. Gear reductions G and G are arranged with ratios such that when rotor R is driven relatively faster [than R the action on the differential will be to rotate arm 49 against stop 51 and open contact 48. This will open the only circuit to line '2 from power source P through lead 85, contact 48, lead 34, lead 97, and contact 27 and the only circuit to line 3 through lead 85, contact 48, lead 84-, lead 59 and contact 28. Opening of contact 48 will thus cut off power supply to lines 2 and 3 regardless of the positions of any other contacts. With lines 2 and 3 de-energized, the offset favorable to balanced traflic is selected as previously explained. This is desirable in many traflic situations.

In other situations it may not be desirable to have the offset automatically change to favor balanced traffic when the system goes onto minimum cycle length. In such cases selector cutout SC would be of no use and could be omitted as shown in the modified circuit of FIG. 2. in this circuit lead 84* feeds power direct from power source P to leads 97 and 59 so the power supply to lines 2 and 3 cannot be interrupted as was done by contact 48 of se lector cutout SC. This leaves the system free to select offsets throughout its range of cycle lengths.

The modification shown by FIG. 3 offers distinct advantages in a common form of traffic problem in the early morning hours frequently beginning at about midnight when traffic is very light. It is a quite common practice at such times to turn all signals to flashing indication but by many authorities a higher speed progressive movement is considered better.

The modified selector cutout MSC as shown in FIG. 3 is the same as the selector cutout SC shown in FIG. 1 except for the contacts and wiring to the contacts. At all cycles except the minimum, stop arm 49 is held against stop pin 56 and contacts 69 and er are held open. On the minimum cycle arm 49 is held against stop pin 51 when contacts so and 61 are in the closed position as shown in FIG. 3.

Contacts 6% and 61 receive energy from power supply P through lead 85. Coil 23 of relay URI is energized through contact 60, lead 107 and lead 32. Coil 24 of relay LRO is energized through contact 61, lead 108, and lead $3. When coil 23 is energized, contact 27 is closed which energizes line 2 from power supply P through lead @4 lead 97, and contact 27. Similarly when coil 24 is energized, contact 28 is closed and energy from power supply P is fed through lead 84*, lead 59 and contact 28 to line 3. Parallel circuits are carried through separate contacts as and 61 to avoid feedbacks. When lines 2 and 3 are both energized, an offset favorable to light traffic is selected which makes speed control possible with full signal protection and unnecessary speed restrictions.

At the bottom of FIG. 3 is shown a typical pair of selector relays. The coil of relay S is connected to line 2 by tap 2 and the coil of relay S is connected to line 3 by tap 3 in the circuit as shown relays S and S are both energized. Under this condition energy is fed from power supply P through lead 103, contact 62, lead it?!) and contact 66 to line L which is the condition for selecting the offset favorable to light traffic. i

The conditions under which lines 2 and 3 are energized and dc-energized have been explained. Relays S and S could equally well be connected to lines 2 and 3 of FIG. 1. If neither S nor S is energized, line B will be energized from power supply P through lead 103, contact 63, lead 99 and contact 65 which is the condition for selecting the offset favorable to equally divided trafiic. If relay S only is energized, line I will be energized from power supply P through lead 103, contact 62, lead fill? and contact 6'7. This will select the offset favoring inbound traffic. If relay S only is energized, line will be energized from power supply P through lead 163, contact 63, lead 9 and contact 64. This will select the offset favorable to outbound traffic.

FIG. 4 is a modification of FIG. 3 in which it will be observed that the power supplies to coils 96 and 98 have been reversed. Coil 96 is now energized directly from power supply P through lead 38 coil 96 and lead 86*. Coil 98 is now energized from power supply P through lead 78 coil 98, and lead 79 Power supply P is constant so rotor R is now driven at constant speed. Power supply P is variable in proportion to the system cycle length. Rotor R is geared through reduction gear G to act on differential 35 with a speed a little less than the maximum speed exerted by rotor R At all system cycle lengths less than the maximum rotor R will be driven faster than rotor R so will exert a torque on differential 35 to rotate arm 49 against stop 54} which will hold contacts 60 and '61 open so they will be ineffective. At maximum system cycle length rotor R will be driven slower than rotor R so will exert a torque on differential 35 to rotate arm 49 against stop 51 which will close contacts 69 and 61. This is the condition for energizing line L which in this case would be used to select an offset favorable to very heavy trafiic. This is usually the so-called stop-and-go offset which permits all traffic north and south, for example, to move for a period after which it stops and all east and west trafiic moves for a period.

Referring now to FIG. 5, a schematic diagram is shown in block form with equipment of FIG. 1 associated with other units to form a complete signalling system.

At the top of FIG. 5 is represented a highway with a detector DI in one lane of travel.

Below the highway is represented a master controller MC which may be of any of the various types for maintaining the cycle length of the system. Running out from MC are two lines A and B which, for example, I have chosen as two supervisory wire connections as shown in a preferred form of control in my Patent No. 2,657,375. Any of various forms of supervisory control may be employed. Some use more than two interconnecting wires, some use a single interconnecting wire and some use radio transmission which requires no interconnecting wires at all.

Below and to the right of master controller MC is offset controller OC. Input from lines A and B is fed through taps 118 and 111 to calculating timer CT and selector cutout SC. Output from calculating timer CT feeds sampling timer ST through connection 119. Sampling timer ST feeds offset selector OS through connection 112. Output from detector DI is fed to offset selector OS through connection 113. Output from offset selector OS is fed to latch relay LRI through connection 115 and to latch relay LRO through connection 116. Cutout control is fed from selector cutout SC to latch relay LRO through connections 118 and 117 and to latch relay LRI through connections 118 and 121. Output from latch relays LRI and LRO feeds lines 3 and 2 respectively which transmit to local signal controller-s LSC, a sample of one being shown in block form to the right of the offset controller OC in FIG. 5. Feed from lines 2 and 3 is by taps 120' and 122 which go to the local signal controller LSC.

In showing the interconnection between offset controller OC and local signal controller I have used two lines 2 and 3 with two taps 120 and 122. This follows a preferred method disclosed in my Patent No. 2,657,375 but 1G could be by any of various methods using one or more wires or by radio transmission using no wires.

In the block diagram I have indicated a preferred type of local signal controller as disclosed in my Patent No. 2,657,375 but the local controller may be of any type of which several are well known.

In the block diagram suitable power supplies with return circuits are assumed but are not shown.

FIG. 6 shows a modification'of my invention applicable to a system using traffic detector DI for trafiic in one direction in a highway anddetector DO for traffic in the opposite edirection. The two directions for convenience are referred to as inbound and outbound and the respective directions are indicated by arrows.

The modification of FIG. 1 to make FIG. 6 consists of adding connection 164, detector DO, lead 76, time element TEO and lead 77 and eliminating calculating timer CT, cam 33, contact 43 and the connections to these pants consisting of lead '76, tap 72, lead '73, lead 74, lead '75 and lead 71.

Operation of the modified circuit of FIG. 6 is the same as FIG. 1 except that impulses are fed to coil 12 from transformer TR through detector DO, lead 7 6, time delay relay TEO and lead 77 instead of from the calculating timer CT through lead 87. The shading pole pieces of coils 11 and 12 are adjusted for any desired balance between the impulses frorn detectors DI and DO just as a balance is adjusted between the impulses from DI and the calculating timer CT of FIG. 1. Differences in these balances act on the offset selector to select offsets just as described for FIG. 1.

FIG. 7 is a schematic diagram in block form showing the modification of the circuit shown by FIG. 6'. Detectors DO and DI are shown, one in each lane, and are shown feeding into modified offset controller MOC through connections 122 and 1213 respectively. Sampling timer ST is shown also feeding into modified offset selector MOS through connection 124. Modified offset selector MOS feeds latch relays LRI. and LRO through connections 125 and 126 respectively. Lines 3 and 2 are fed by latch relays LRI and LRO respectively. The function of lines 3 and 2 in FIG. 6 is the same as described for FIG. 5.

In the preceding description frequent reference has been rnade to apparatus of a preferred form and material for the drawings has been selected on this basis. Preferred form, however, is to a large extent a matter of opinion in which there may be sound reasons for differences. It will be obvious to those skilled in the art that many substitutions or modifications of equipment in addition to those described could be substituted and still accomplish the results intended by this invention. For example, various means are well known for interval timing which could be substituted for the motors used in the examples such, for example, as timing based on the charge or discharge of condense-rs, timing based on mechanical devices, timing based on changes due to heat or timing based on the escape of gas through an orifice. Well known substitutions could be made for the motors driving cam shafts such as solenoids or pneumatic devices. Substitutions could be made for cams to operate contacts such as solenoids or pnetunatic or hydraulic operated cylinders and devices. In the large variety of well known relays are found substitutes for latch relays, and the field of electrorn'cs provides many timing means and substitutes for electrical contacts.

While a preferred form of apparatus, together with certain possible modifications, is illustrated, this is by way of example only, and various changes in the organization of parts and in details can be made within the principles of the invention and the scope of the claims.

What I claim is:

1. In a trafiic control system having means for selecting the cycle length related to the rate of total trafiic flow on a highway, a device driven by a constant-speed motor establishing successive equal sampling time periods, means to register impulses at equal length from all vehicles passing in one direction over said highway during each of said sampling periods energized by said device driven by said constant-speed motor, a device driven by a motor at a speed variable in proportion to the selected cycle length to produce impulses equally time spaced but variable in length in proportion to the selected cycle, a rotor device connected to be impelled in one direction by said impulses registered by passing vehicles and in the reverse direction by said variable length impulses, and means including selector relays energized by the direction and degree of rotation of said rotor by said opposed impelling forces to select traffic signal offsets, and means in cooperation with said rotor device for returning said rotor device to its initial position after each said sampling period.

2. In a trafiic control system, a device driven by a constant-speed motor establishing successive equal sampling time periods, means energized by said device driven by said constant-speed motor for registe'in" individually impulses of equal length from all vehicles passing in each of two directions on a highway during each of said equal sampling time periods, a rotor device impelled in one direction by the said impulses from ve- JiClGS passing in one direction during one of said sarnpling time periods and impelled in the reverse direction by said impulses from vehicles passing in the reverse direction during the said sampling time period, electrical contacts to select traffic signal offsets, and said contacts being actuated :by the direction and degree of rotation of said rotor deviceby said opposed impelling forces.

3. Apparatus as defined in claim 2 wherein said rotor device includes means for periodically returning all parts to a definite re-starting position, after each said sampling time.

4. A trams cycle offset selector mechanism for use with means for determining trafiic volume in both directions along a roadway and developing an output signal proportional thereto, including sampling timer means for determining the duration of successive intervals for sampling traffic volume, offset selector means, a timing element connected to said sampling timer means and energized thereby for energizing said offset selector means during said sampling interval, a calculating timer energized from said output signal, a traffic actuable detector in one lane of said roadway for actuating said time element, said offset selector means being actuated, proportional to the traffic volume, by said time element in one direction and by said calculating timer in the opposite direction, a first offset selector circuit energized by said offset selector means when it is energized beyond a predetermined position in one direction by said time element, and a second olfset selector circuit energized by said offset selector means when it is energized beyond a predetermined position in the other direction by said calculating timer.

'5. A trafiic offset controller mechanism adapted to utilize a cycle-length-determining signal from a master controller and to energize one of a plurality of offset elector circuits, including a calculating timer energized by said cycle-length-determining signal, a traffic detector actuated by the volume of trai'lic in one direction, a timer element initiating a cycle of operation with each actuation of the traflic detector, at sampling timer to determine the duration of a traffic sampling period, an offset selector moved by said calculating timer and said timer element into one of a plurality of positions during a sampling period, said sampling timer setting said 'ofiset selector back to a zero position at the end of said sampling period, a first latch relay energized to, and latched in, one position by said offset selector when the latter is energized to a first position, a second latch relay energized to, and latched in, one position by said otfset selector when the latter is ener ized to a second position,

and offset selector circuits energized by said latch relays when the latter are latched.

6. An offset selector mechanism having an integrator including a disc and at least first and second driving coils adapted to rotate said disc in opposite directions, a shaft rotated by said disc carrying a plurality of cams, contacts adjacent said cams adapted to be closed thereby upon sufficient rotation of said cam shaft in one or the other direction, first and second coil-energizing timers connected respectively to said first and second driving coils, a source of local power and a source of variable voltage power, said first coil-energizing timer connected to said source of variable voltage power and consisting of a synchronous motor driven cam and contact arrangement adapted to apply local power to said first coil at equally spaced intervals whose duration i inversely proportional to said variable frequency, a traffic aetuable detector in one lane of a roadway, said second coilenergizing timer connected to said detector and to a source of local power and adapted to apply local power to said second coil during each actuation of said detector and for an interval thereafter, a plurality of local traffic signal controllers each having a plurality of offset controls, and an interconnection between said offset controls and said contacts controlled by said integrator.

7. In a mechanism as in claim 6, a sampling interval timer energized from local power and having a first cam and contact arrangement connected to apply power from said variable voltage power source to said synchronous motor at equally spaced intervals, third and fourth contact arrangements adjacent third and fourth half cams on said disc rotated shaft, third and fourth driving coils adapted to home said disc in opposite directions, said sampling interval timer having second and third cam and contactarrangements connected to apply local power to said third or fourth driving coil through said third or fourth contacts adjacent said disc-rotated shaft to thereby home said disc at intervals longer than a traflic signal cycle.

8. A trafiic cycle offset selector for use in a trafiic control system having a remote traffic cycle length selector which develops an output frequency inversely proportional to total traffic volume on a thoroughfare, said traffic cycle off-set selector including in combination, an impulse generator adapted to receive variable frequency power from the remote traffic cycle length selector, a source of local power, said impulse generator consisting of a synchronous motor started at uniform intervals and having a cam and first contacts closed thereby to apply said variable frequency power to said motor for an in terval dependent upon the speed of said motor, second contacts also closed by said cam simultaneously with said first contacts, an integrator comprising a disc connected to rotate a cam shaft, at least two driving coils adjacent said disc, one connected to receive local power through said second contacts and said second connected to receive local power through a trafiic responsive timer, said traffie responsive timer connected to be energized from local power through closure of contacts of a traffic actuated detector mounted along trafiic path and connected to maintain itself energized for a time thereafter and while energized to apply local power to the second of said driving coils, cams on said cam shaft controlled by said disc integrator, at least first and second contacts controlled by said cams, first and second offset control lines, said first line connected to be energized through said first contacts when said disc integrator is rotated far in a first direction, said second line connected to be energized through said second contacts when said disc integrator is rotated far in the opposite direction, and off-set control mechanism at a plurality of local controllers connected to be controlled by said first and second lines.

9. A traffic cycle offset selector as in claim 8, including at least two homing coils adjacent said integrator disc, third and fourth cams on said cam shaft controlled by 13 said disc, an interval timer having a plurality of cams and contacts arranged to energize one or the other of said homing coils through said third or fourth cams depending upon the position of said cam shaft, said interval timer arranged to close its said contacts at intervals greater than one traffic signal cycle.

10. In a traffic cycle offset selector for use on a highway having inbound and outbound trafiic lanes; traffic actuable detectors in at least one inbound and at least one outbound lane, two time delay relays each one connected to a source of power and to one of said detectors and each of said delay relays adapted to pass power for a fixed time after the detector to which each said delay relay is respectively connected is actuated, an electro mechanical totalizing device having at least one pair of drive coils, one of each pair of said coils connected to one of said delay relays, and the other of said coils connected to the other delay relay and adapted to drive said device in opposite directions, at least two pairs of contacts operable by said device, one of said contact pairs operated by said device when it reaches a limiting position in one direction, another of said contact pairs operated by said device when it reaches a limiting positionin the opposite direction, a pair of latch relays each one connected to said source of power through one of said contact pairs, each of said latch relays having an output circuit energized from local power while said relay is latched, a plurality of local traffic signal controllers each having inbound and outbound offset control means individual to a direction of traffic, said inbound offset control means energized through one of said latch relays when said totalizing device is rotated to its limiting position by power from said inbound detector and timer, said outbound offset control means energized through the other of said latch relays when said totalizing device is rotated to its limiting position by power from said outbound detector and timer.

11. An improved traffic cycle offset selector as in claim said totalizing device having a pair of reset coils, one of said pair connected to drive said device in a direction opposite the other of said pair, a pair of reset cams and contacts controlled thereby, one or the other of said reset coils connected through said reset contacts depending on the over-center position of said totalizing device, an interval timer connected to said source of power and having a plurality of cams and contacts controlled thereby to apply power to said reset contacts at intervals to thereby reset said totalizing device.

12. For use in a traffic control system having means for selecting cycle length related to the rate of total traffic flow 'on a highway and circuit means for effecting the cycle length selected, a traffic signal offset selector, including: a device driven at a constant speed for establishing successive equal sample time periods; means cyclically energized by said constant speed device for registering impulses of equal duration from substantially all vehicles passing in one direction over said highway during one of said sample time periods; a device driven at a speed variable in proportion to the selective cycle length providing impulses equally time spaced but variable in length in proportion to the selected cycle; rotor device impelling means connected to said means to register impulses from said passing vehicles and also connected to receive said variable and length impulses; a rotor device adapted to be impelled by said impelling means in one direction by said impulses registered by said passing vehicles and in the reverse direction by said variable length impulses; and means including electrical contacts actuated by the direction and degree of rotation of said rotor by said impelling means to select traffic signal offsets.

13. Apparatus as defined in claim- 12 in which said rotor device includes means for periodically returning all parts to a definite re-starting position, after each successive equal sample time period.

14. In an offset controller mechanism adapted to utilize a cycle length determining signal from a master controller and to energize one of a plurality of ofiset selector circuits, including: a calculating timer energized by said cycle length determining signal; a trafiic detector actuated by traffic flow in one direction along a thoroughfare; a timer element started through a cycle of operation with each actuation of said trafiic detector; an offset selector energized by said calculating timer and said timer element into one of a plurality of positions during a sampling period; a sampling timer for determining the duration of said sampling period and connected to energize said offset selector back to a zero position at the end of said sampling period; a first latch relay energized and latched into one position by said offset selector when said offset selector is energized into a first position; a second latch relay energized and latched into one position by said offset selector when said offset selector is energized into a first position, and said offset selector circuits energized by said latch relays when said relays are latched.

15. A traffic cycle offset selector for use with apparatus for determining traflic volume in both directions along a roadway and developing an output signal proportional thereto, including: rotatable offset selector means energized during a sampling interval, said rotatable offset se lector means having a plurality of positions including a zero position; a time element actuated by a traflic actuable detector along one lane of said roadway connected to said rotatable offset selector means; a calculating timer energized from said signal proportional to traffic volume also connected to said rotatable offset selector means; a first offset selector circuit energized by said offset selector means when said means is energized over its zero position by said time element, and a second offset selector circuit energized by said offset selector means when said means is energized over its zero position in the other direction by said calculating timer.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Automatic Signal Division, Eastern Industries, Bulletin E-224, copyright 1956.

Inc., 

1. IN A TRAFFIC CONTROL SYSTEM HAVING MEANS FOR SELECTING THE CYCLE LENGTH RELATED TO THE RATE OF TOTAL TRAFFIC FLOW ON A HIGHWAY, A DEVICE DRIVEN BY A CONSTANT-SPEED MOTOR ESTABLISHING SUCCESSIVE EQUAL SAMPLING TIME PERIODS, MEANS TO REGISTER IMPULSES AT EQUAL LENGTH FROM ALL VEHICLES PASSING IN ONE DIRECTION OVER SAID HIGHWAY DURING EACH OF SAID SAMPLING PERIODS ENERGIZED BY SAID DEVICE DRIVEN BY SAID CONSTANT-SPEED MOTOR, A DEVICE DRIVEN BY A MOTOR AT A SPEED VARIABLE IN PROPORTION TO THE SELECTED CYCLE LENGTH TO PRODUCE IMPULSES EQUALLY TIME SPACED BUT VARIABLE IN LENGTH IN PROPORTION TO THE SELECTED CYCLE, A ROTOR DEVICE CONNECTED TO BE IMPELLED IN ONE DIRECTION BY SAID IMPULSES REGISTERED BY PASSING VEHICLES AND IN THE REVERSE DIRECTION BY SAID VARIABLE LENGTH IMPULSES, AND MEANS INCLUDING SELECTOR RELAYS ENERGIZED BY THE DIRECTION AND DEGREE OF ROTATION OF SAID ROTOR BY SAID OPPOSED IMPELLING FORCES TO SELECT TRAFFIC SIGNAL OFFSETS, AND MEANS IN COOPERATION WITH SAID ROTOR DEVICE FOR RETURNING SAID ROTOR DEVICE TO ITS INITIAL POSITION AFTER EACH SAID SAMPLING PERIOD. 